Digestion
The horse is a non-ruminant herbivore that has evolved to eat small, frequent meals by grazing for up to 18 hours a day. By looking at how the horse’s digestive system works we can better understand our horse’s needs with regard to feeding.
The process of digestion starts with the teeth, the horse will use its lips, teeth and tongue to grasp grass, this requires the horse to make a full long jaw sweep which wears the teeth more evenly, however this does not occur when the horse is eating concentrate feed when only a shorter jaw sweep is required. Teeth should be regularly checked and treatment carried out if necessary to prevent sharp edges forming.
Chewing stimulates the production of saliva which is then mixed with the food to aid the passage of food down the oesophagus, which is a simple muscular tube linking the mouth to the stomach. Feed that has not been chewed properly (another reason for having your horse’s teeth checked) or has not been mixed with adequate saliva can become lodged in the oesophagus causing choke. Adding chaff and water to your feed can help to prevent your horse eating too quickly and reduces the risk of food becoming stuck because it is not lubricated enough.
Food is then passes into the stomach which is relatively small and most efficient when it is two thirds full, it is important not to feed more than 2kg of concentrate food per meal, or even less for small ponies. Feeding little and often helps guard against gastric ulcers which can occur when the stomach is empty – allowing gastric acid which is produced continuously to ulcerate the upper part of the stomach which does not possess a protective coating. While in the stomach food is mixed with acids and enzymes that help to break it down, although little of the feed nutrients are absorbed in the stomach.
Food then passes into the small intestine where the majority of feed nutrients are digested and absorbed including carbohydrates, proteins, fat soluble vitamins A D E and K and some minerals. Feed passes through the stomach and small intestine rapidly and if too large meals are fed this can overload the small intestine causing them to pass into the large intestine resulting in a build up of gas and lactic acid which can cause colic or laminitis.
Digestion in the large intestine or hindgut is carried out by ‘friendly’ bacteria which break down plant fibres and undigested starches into volatile fatty acids which are a source of nutrients and energy for the horse.
Feed first enters the caecum where undigested food from the small intestine such as grass and hay are broken down by bacteria. The caecum is unusual in that both the entrance and exit are at the top, this is where impactions can occur if a horse eats a lot of dry matter without adequate water. The bacteria in the caecum can only digest certain feed stuffs this is why it is important to make all changes to the diet gradually so that the bacteria has time to adjust. Digestion continues in the large colon and it is here that ‘twisted gut’ can occur, as the series of pouches that make up the large colon can become twisted and fill with gas due to the fermentation of the feed. By the time feed reaches the small colon the majority of nutrients have been extracted from it, and the function of the small colon is to reclaim any excess moisture, which results in faecal balls being formed which are then passed to the rectum and expelled.
When feeding our own horses it is important to bear in mind the horse’s digestive system and how they have evolved as ‘trickle’ feeders. By mimicking the horse’s natural diet and feeding patterns we can go some way to avoiding many digestive problems.
Digestion
Gastric Ulcers
Health
Intolerance & Allergies
Laminitis
Winter Feeding
